The interior of an automobile is normally insulated from sounds which are transmitted through the frame of the automobile, these sounds originate from tires, road noises, wind noises, engine noises, and noise from the other mechanical parts of the automobile. Numerous substrates are known in the art for abating sound from the exterior of an automobile to the interior of an automobile. For example, it is known in the art to provide for a fibrous material between the exterior noise and the interior of the automobile. The material dampens the sound transmissions and vibrations. There are a wide variety of damping materials known in the art, for example, non-woven textile fabrics, such as shoddy pads, and foamed polyurethane materials. It is also known in the art to apply an acoustical insulating barrier to the damping material via glue. Such an application normally occurs in the carpet of an automobile. See for example, U.S. Pat. Nos. 4,056,161; 4,966,799; 5,266,143; and 5,068,001. However, such acoustical damping materials are heavy.
Additionally, it is known in the art to produce a needled composite acoustical barrier, which limits the need for glues. See for example, U.S. Pat. No. 6,109,389. Additionally, it is known in the art to provide a panel or similar element with structural and acoustical properties formed of a cellular core coated on both sides with skins made of fabric plies of mineral or synthetic fibers impregnated with a thermoplastic resin, which is able to resist significant loads and perform acoustical attenuations. See for example, U.S. Pat. No. 5,888,610.
Also, there are two processes known in the art for preparing dashboard insulation that is mounted on the firewall of the automobile to shield and or absorb noise stemming from the engine. Generally, these dashboard barriers include a vacuum formed heavy layer bariumsulfate filled EVA or PVC or an injection molded TPO skin and a decoupler such as, a cast polyurethane foam, skived polyurethane foam, fiber mats made from polyester or natural fibers and shoddy pads. In the case of fiber mats, a phenolic binder is applied.
The process for the manufacture of known dashboard insulation involves heating a sheet of vinyl and then transferring the vinyl to a forming tool and subsequently vacuum forming the vinyl. If the barrier is a cast foam, liquid foam is then applied to the tooled vinyl in an open or closed tool operation and then the applied foam is demolded and trimmed. If the barrier is a fiber or a shoddy mat, the formed vinyl is transferred to another forming tool and the fiber or shoddy mat is added and formed and cured.
Barriers formed from this process generally have a double wall effect by decoupling the sound and vibration penetrating through the steel of the firewall from the heavy layer (second wall) by means of a soft flexible, absorptive material such as the foam or mat described above. Barriers containing a resinated phenolic shoddy pad primarily act as absorbers, absorbing sound penetrating through the firewall or sound which is reflected from the passenger compartment.
However, there remains a need in the art for a process to manufacture a three-dimensional molded composite that contains a substrate coated with a polyurethane resin on one side. Specifically, there remains a need in the art to provide lightweight acoustical and structurally sound three-dimensional insulation parts for automobiles.